1. Field
Example embodiments relate generally to wireless transmission systems, and particularly to estimating lag in a cable between a remote radio head and an antenna.
2. Related Art
Lag estimation methods can be used to measure lag based on an estimate of the arrival of the reflected signal upon the transmission of the wireless communication signal in a transmitter. The lag to be estimated may be the difference between the transmitted signal transmitted from a remote radio head (RRH) over an antenna feeder cable and the reflected signal received at the RRH due to the imperfections at the antenna end of the feeder cable. The lag can be measured by either measuring the phase of the reflected received wireless signal or directly measuring its arrival time. The estimation techniques of lag measurement can be classified into three classes as narrowband, wideband and ultra wide band (UWB).
The pseudo-noise (PN) sequence wideband signal has been used for estimation of the lag. In such a system, a signal coded by a known pseudo-noise (PN) sequence is transmitted by a transmitter. The received reflected signal is matched with the locally generated PN sequence. The lag between the transmitted and the received reflected signal is determined from the computed arrival time. In PN sequence systems because of the processing gain at the receiver, the PN sequence lag estimation systems perform much better than other systems in suppressing interference.